Error exiting Python after importing pymt

[mdpiper]

After quitting a Python session in which pymt was imported, an error message is shown.

To reproduce:

1. Make a new conda environment and activate it.

$ conda create -n pymt -c conda-forge python=3 pymt
$ conda activate pymt

2. Start a Python session, import pymt, then kill the session, noting the error message.

$ python
Python 3.9.6 | packaged by conda-forge | (default, Jul 11 2021, 03:36:15)
[Clang 11.1.0 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pymt
>>> ^D
Error in sys.excepthook:

Original exception was:

There's no body in the message.
The message only appears in Python, not IPython.
I'm using pymt=1.3.1.